1. Field of the Invention
The present invention relates to structural foundations including earth anchors for supporting airport and roadway signs, utility poles, communication towers, and the like and installation apparatus and methods for such structural foundations.
2. Background
By conventional methods, a concrete foundation, also called a concrete pier or pad, is utilized for the installation of various types of structures, e.g., signs, high mast lighting and utility poles, communications towers, and the like. A concrete pad or pier is utilized for its mass to provide a structural foundation for supporting such structures.
These structures are attached to the concrete pier or pad by means of bolts or threaded anchors which are set to the required elevation in a rebar cage prior to pouring the concrete in forms.
In the installation of such a concrete pier or pad by the conventional method, site layout is performed, equipment is deployed, the site is excavated, the spoils are removed, and a stone sub-base sometimes is placed in the excavated hole. The work requires a backhoe, a truck, and equipment operators as well as the engineer and one or more laborers depending on the size of the job. Materials, such as the stone for the sub-base, are also required. In the case of some installations, e.g., in airport runway work, all construction debris and equipment must be removed from the work site by the end of each work day.
Then pouring forms are built, a rebar mat is installed, bolts or threaded anchors are attached to the rebar at the required elevation, and the concrete pad is poured. This work requires a carpenter, a laborer and the material, i.e., concrete, forms, test equipment, bolts, and rebar mats. Again, in the case of airport runway work, all construction debris and equipment must be removed from the site at the end of the work day.
Next, the forms must be stripped, and back-filling around the foundation takes place. This work requires a backhoe, the operator, a carpenter, a laborer, and materials used to back-fill and seed the area.
The conventional method requires the concrete to cure for about seven (7) days. This concrete curing sometimes takes longer depending on the type of concrete used. If testings show the concrete not to comply with a specified strength within the first seven (7) days, then it is required to wait twenty-eight (28) days before any structure can be installed upon the concrete.
Bolts or threaded anchors are used for the installation of structures on the foundation. The structures are installed after the concrete has cured. Accordingly, several days are required to install the concrete foundation and to place the structures into operation.
In the case of airport runway work, on the eleventh day, the concrete pad is drilled to provide holes for the installation of the concrete anchors. These concrete anchors are utilized for the installation of the anchor bolts which will be used for installing the airport runway sign upon the foundation. The sign then is installed and energized at this time through work performed by electricians. Accordingly, eleven days have been required to install and illuminate the airport runway sign.
From the description of the conventional method of installation for a structure supported by a concrete foundation, some of the major drawbacks of the conventional installation method are apparent. These drawbacks include prolonged roadway area closure time in the case of a roadway sign, utility pole, or high mast lighting pole, prolonged runway and taxiway closure time in the case of airport signs, and lengthy installation times. These drawbacks further include increased labor costs, weather dependent operation, and an increased risk of debris falling on the roadway or aircraft traffic areas (in the case of airport installations) attributable to the many truck trips required. These drawbacks and others are eliminated or substantially reduced by installing a metal sign or utility pole foundation.